Re: [15/17] SLUB: Support virtual fallback via SLAB_VFALLBACK

From: Peter Zijlstra
Date: Fri Sep 28 2007 - 13:59:32 EST

On Fri, 2007-09-28 at 10:33 -0700, Christoph Lameter wrote:

> Again I have not seen any fallbacks to vmalloc in my testing. What we are
> doing here is mainly to address your theoretical cases that we so far have
> never seen to be a problem and increase the reliability of allocations of
> page orders larger than 3 to a usable level. So far I have so far not
> dared to enable orders larger than 3 by default.

take a recent -mm kernel, boot with mem=128M.

start 2 processes that each mmap a separate 64M file, and which does
sequential writes on them. start a 3th process that does the same with
64M anonymous.

wait for a while, and you'll see order=1 failures.

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